1. Field of the Invention
The present invention relates to a method for producing an alloy catalyst for redox reaction used as, for example, an electrode catalyst for a hydrogen-oxygen fuel cell.
2. Description of the Related Art
Conventionally, there is known a hydrogen-oxygen fuel cell equipped with an electrolyte layer sandwiched by a pair of electrode catalyst layers. In the hydrogen-oxygen fuel cell, when e.g. a hydrogen gas is introduced as a reducing gas to an anode electrode, the hydrogen gas generates protons by the action of the catalyst in the electrode catalyst layer, as is shown in formula (1). The generated protons move to the electrode catalyst layer on a cathode electrode side via the electrolyte layer.
On the other hand, when the hydrogen gas is introduced to the anode electrode and e.g. an oxygen gas is introduced as an oxidation gas to the cathode electrode, the protons generate water by reacting with the oxygen gas by the action of the catalyst in the electrode catalyst layer on the cathode electrode side, as is shown in formula (2). Thus, by connecting the cathode electrode and the anode electrode with a conducting wire, an electric current can be taken out. At this time, each electrode catalyst layer acts as a catalyst for redox reaction for generating the reactions of the formulae (1) and (2).Anode electrode: 2H2→4H++4e−  (1)Cathode electrode: O2+4H++4e−→2H2O  (2)
As this type of catalyst for redox reaction, a platinum catalyst is known, but the platinum catalyst is expensive and thus a decrease of an amount of the platinum used is desired. Thus, as a catalyst for redox reaction decreasing the amount of the platinum used, a platinum-nickel alloy catalyst is suggested (for examples, refer to Japanese Patent Laid-Open No. 64-45061). According to an X-ray diffraction, it is said that this platinum-nickel alloy catalyst contains approximately 50 atomic % of nickel in the alloy and has a particle diameter of 4.8 nm. Further, it is said that this platinum-nickel alloy catalyst has 1.4 times higher catalytic activity than a platinum catalyst having a same mass.
However, for an alloy catalyst for redox reaction, it is desired that the catalyst has a better catalytic activity.
Thus, in view of such circumstances, an object of the present invention is to provide a method for producing an alloy catalyst for redox reaction which is capable of obtaining a better catalytic activity than that of the conventional platinum-nickel alloy catalyst. Another object of the present invention is to provide a method for producing a carbon powder supporting an alloy catalyst for redox reaction in which the alloy catalyst for redox reaction is supported on the carbon powder.